Issue |
A&A
Volume 365, Number 3, January IV 2001
|
|
---|---|---|
Page(s) | 465 - 475 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20000146 | |
Published online | 15 January 2001 |
HD 172481: A super lithium-rich metal-deficient post-AGB binary with a red AGB companion*
Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200B, 3000 Leuven, Belgium
Corresponding author: M. Reyniers, maarten.reyniers@ster.kuleuven.ac.be
Received:
29
June
2000
Accepted:
16
October
2000
We present in this paper a study on the peculiar supergiant HD 172481. Its spectral
type (F2Ia), high galactic latitude (b = -10 fraction of degree37), circumstellar dust, high
radial velocity and moderate metal deficiency ([Fe/H] = -0.55) confirm the
post-AGB character of this object. A detailed chemical analysis shows slight but
real s-process overabundances, however no CNO-enhancement was detected. Furthermore,
the spectral energy distribution and the TiO bands in the red part of the spectrum
reveal a red luminous companion. The luminosity ratio of the hot F type component
and this cool M type companion is derived for a reddening of
(
) and indicates that the companion
must also be strongly evolved and probably evolving along the AGB. Neither our
photometric data-set, nor our radial velocity monitoring show evidence for orbital
variability which may indicate that the period is too large for direct binary
interaction. Most interestingly, a strong lithium resonance line is detected, which
yields an abundance of
= 3.6. Several explanations for
this large lithium content are explored.
Key words: stars: abundances / binaries: spectroscopic / stars: chemically peculiar / stars: individual: HD 172481 / stars: AGB and post-AGB / stars: evolution
© ESO, 2001
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